Exercise Armageddon, also described as Operation Armageddon, were plans by the Republic of Ireland drafted in September–October 1969 that envisaged a military invasion and guerilla operations in Northern Ireland during The Troubles, in order to protect the Catholic communities during rioting.
The Northern Ireland Civil Rights Association organised protest marches from 1968 seeking to improve conditions for Roman Catholics in Northern Ireland, who were discriminated against by the majority Protestant population. This had led to counter-protests and then sectarian riots, leading to 1,500 Catholic refugees moving south to the Republic of Ireland. The Government of the republic wanted to help in some way, and on 13 August 1969 the Taoiseach, Jack Lynch said in a television interview: "...the Irish government can no longer stand by and see innocent people injured and perhaps worse". His cabinet was divided over what to do, with Kevin Boland and Neil Blaney calling for robust action. On 30 August Lynch ordered the Irish Army Chief of Staff, General Seán Mac Eoin, to prepare a plan for possible incursions.
While the riots continued, the introduction of British Army troops in the Falls area of Belfast, and around the Bogside part of Derry from mid-August under Operation Banner protected the Catholic communities from further such attacks. Therefore the planning of Exercise Armageddon into October 1969 was superseded by events and did not reflect the reality on the ground.
The army's planners accepted that it had "no capability to engage successfully in conventional, offensive military operations against the security forces in Northern Ireland" to protect the Catholic minority from loyalist mobs.
The plan called for units of specially trained and equipped Irish commandos to infiltrate Northern Ireland and launch guerilla-style operations against the Belfast docks, Aldergrove airport, the BBC studios and key industries. The campaign would start in Belfast and the northwest, so as to draw the bulk of security forces in Northern Ireland away from the border areas and turn their attention to the guerrilla campaign. The Irish Army would then invade with four brigades operating in company-strength units to occupy the Catholic areas of Derry and Newry, and attack any remaining security forces in those areas. The Irish Army Transport Corps did not have enough resources to transport all of the necessary forces to the conflict zone, and the plan suggested hiring buses from Córas Iompair Éireann. As an element of surprise was required, Ireland would not formally declare war when the operation started.
However the planners also accepted that only 2,136 troops out of 12,000 in the army were at actual combat readiness. The operation would leave the Republic of Ireland exposed to "retaliatory punitive military action by United Kingdom forces". The plan included a warning that: "The Defence Forces have no capability of embarking on unilateral military operation [sic] of any kind ... therefore any operations undertaken against Northern Ireland would be militarily unsound."
- The plan to occupy Newry would not save any Catholic refugees, as it was a predominantly Catholic town with no inter-sectarian riots.
- The Catholic parts of Derry had suffered assaults from the Royal Ulster Constabulary and Protestant mobs, but was effectively ring-fenced on the introduction of British troops in August; as of October 1969, further attacks were unlikely.
- The plan ignored the incompatibility of forces. Britain was a member of NATO, while the Irish Defence Forces were much smaller than the British Armed Forces, had inferior arms and transportation in comparison to British forces, and had only minimal Air and Naval capabilities. The Defence Forces were said to train for "World War II operations using World War I weapons", such as the Lee-Enfield rifle, although most Irish soldiers were armed with FN FAL 7.62 automatic rifles. The Irish Army also had some motorized transport, and the Irish Army Cavalry Corps generally had a low number of light armored vehicles. The Irish Air Corps had approximately half a dozen serviceable de Havilland Vampire jets, and the Irish Army Artillery Corps had only heavy mortars and some WWII-era howitzers. By contrast, British forces in Northern Ireland consisted of almost 3,000 heavily armed soldiers of the 2nd Queens Regiment, the Royal Regiment of Wales, and the Prince of Wales's Own Regiment of Yorkshire. These troops had considerable experience in training and conventional large-scale combat tactics, and many had returned from guarding NATO's Northern Flank. They were equipped with Humber Pig and Saracen armored personnel carriers. Royal Air Force F-4 Phantom and Harrier jets were also stationed at airbases close to Northern Irish airspace. These forces would have been capable of dealing decisively with any Irish military incursion into the area. The mismatch was reflected in the choice of title. According to security analyst Tom Clonan, "irrespective of the element of surprise, the Irish Army would have been subject to a massive British counterattack - probably within hours of their initial incursion. Irish casualties would have been high as the British would have sought to swiftly and indiscriminately end the Republic's unilateral military intervention".
- In 1969, both Ireland and Britain were applying to join the EEC. Ireland's application would likely have been jeopardised if it had invaded a "friendly neighbour".
- While the Irish government had called for United Nations involvement in Northern Ireland in August 1969, launching a localised but technical invasion and then calling again for intervention would have led to universal condemnation, being contrary to international law. Ireland had joined the UN only in 1955.
- All members of NATO are bound by its treaty to oppose a military incursion on a member state; this would probably force the United States to intervene.
- The targets for covert operations, such as the BBC offices in Belfast, were already guarded by the British Army to protect them from local rioters. None of these targets were linked to the inter-sectarian riots.
- An intrusion might have provoked new and more widespread sectarian rioting, causing hundreds of deaths.
- Former Irish officers such as Vincent Savino recalled that the army was "so short of the basics", having been allowed to run down since 1945 by the same politicians who now wanted it to undertake such a dangerous mission.
- There was a high chance that the British forces and UK government would counter the invasion with a counter-invasion of the Republic, most likely resulting in the capitulation of the Republic to UK forces in a hypothetical retaliatory invasion and occupation.
Historian Diarmaid Ferriter considers that the operation would have been popular at the time, given the strong emotive feeling in the Republic about the situation in Northern Ireland.
Subsequently some more actively nationalist Irish Ministers were tried in 1970 in the Arms Crisis trial, where the defendants included an Irish army officer. It emerged that a secret Irish government fund of £100,000 had been dedicated to helping the refugees, but some of it had been spent covertly on buying arms for paramilitary groups. Ministers Charles Haughey and Neil Blaney were sacked from their posts.
- The army's 1969 memo was declassified in 2004 according to the documentary, but according to an article in the Irish Independent, at least the handwritten version was released in 2001.
- The Irish Times, 31 August 2009, p.13.
- Clonan, Tom. "'Operation Armageddon' would have been doomsday - for Irish aggressors", The Irish Times, 31 August 2009. Retrieved 3 September 2009.
- The Sunday Times (Irish edition), 30 August 2009, p.4.
- Burns, John. "Irish army plotted Belfast guerrilla war", The Sunday Times, 30 August 2009. Retrieved 3 September 2009.
- The Irish Times, op. cit.
- "If Lynch Had Invaded", RTÉ Television.
- Downey, James. "Army on Armageddon alert", Irish Independent, 2 January 2001.